"Good building" does not mean person got enough fingermuscles to hold hook down enough time to queue 600 tidals. Good building means effective building, it means that in given time good builder can get more units out of his factories than his opponent. If success in building is good enough, there's no need for any "slightly above braindead"- level of uc. 10 flash beats 1 flash if youre smart enough to not put those 10 on hold fire.
Type ".total" few times during this demo and you can see how deadly better planning can be in maps like this.
Note: I don't rate players to hide outcome. They simply got same raiting than game.